then you might want to set up Guzzle (PHP HTTP client and framework) and Goutte (screen scraping and web crawling library for PHP) in a way that it ignores strict SSL rules.

When you use Mink Goutte browser emulator it uses Guzzle to make requests and that actually uses cURL to archive that. To pass cURL parameters to Goutte you need to add them into curl.options section of default/extensions/Behat\MinkExtension\Extension/goutte/guzzle_parameters. You will need to set ssl.certificate_authority to system as well, otherwise the Guzzle\Http\Client::initSsl will reset CURLOPT_SSL_VERIFYHOST and CURLOPT_SSL_VERIFYPEER parameters to some other values.